基于plc的排水系統控制設計-畢業論文-資料下載頁

　　

【正文】 1994，7．[3] 王常力．工業控制計算機的現狀與發展[J]．自動化博覽，1997，9．[4] 王兆義． 可編程控制器的發展動向[J]．電氣自動化，1998，4．[5] 廖常初．可編程序控制器應用技術[M]．重慶：重慶大學出版社，2022，7．[6] 王金全， 方忠華，仲未央．工業控制系統的現狀與展望[J ]．中國電力報，1998，1．[7l 王常力，廖道文．集散型控制系統的設計與應用 [M]．北京：清華大學出版社，1993，6．[8] Bryan, . and Bryan, . 1988. Programmable Controllers Theory and Implementation 1st ed. Atlanta, Geia: Industrial Text Co. 鞍山科技大學本科生畢業設計(論文) 第 27 頁 鞍山科技大學本科生畢業設計(論文) 第 28 頁附錄 A Introduction of Programmable ControllersOverview A PLC (Programmable Controller) is basically a CPU (Central Processing Unit) containing a program and connected to input and output (I/O) device. The program controls the PLC so that when an input signal from an input device turns ON, the appropriate response is made. The response normally devices could be photoelectric sensors, pushbuttons on control panels, limit switches, or any other device that can produce a signal that can be input into the PLC. The output devices could be solenoids, switches activating indicator lamps, relays turning on motors, or any other devices that can be activated by signals output from the PLC.For example, a sensor detecting a passing product turns ON an input to the PLC. The PLC responds by turning ON an output that activates a pusher that pushes the product onto another conveyor for further processing. Another sensor, positioned higher than the first, turns ON a different input to indicate that the product is too tall. The PLC responds by turning on another pusher into a rejection box. Although this example involves only two inputs and two outputs, it is typical of the type of control operation that PLC can achieve. Actually even this example is much more plex than it may at first appear because of the timing that would be required, . “How does the PLC know when to activate each pusher?” Much more plicated operations, however, are also possible. The problem is how to get the desired control signals from available inputs at appropriate times. To achieve proper control, the C200H uses a form of PLC logic called ladderdiagram programming. This manual is written to explain ladderdiagram programming and to prepare the reader to program and operate the C200H.The Origins of PLC logicPLC historically originate in relaybased control systems. And although the integrated circuits and internal logic of the PLC have taken the place of the discrete relays, timers, counters, and other such devices, actual PLC operation proceeds as if those discrete devices were still in place. PLC control, however, also provides puter capabilities and accuracy to 鞍山科技大學本科生畢業設計(論文) 第 29 頁achieve a great deal more flexibility and reliability than is possible with relays.The symbols and other control concepts used to describe PLC operation also e from relaybased control and form the basis of the ladderdiagram programming method. Most of the terms used to describe these symbols and concepts, however, have e in from puter terminology.PLC Terminology Although also provided in the Glossary at the back of this manual, the following terms are crucial to understanding PLC operation and are thus explained here.(1) PLC Because the C200H is a Rack PLC, there is no one product that is a C200H PLC. That is why we talk about the configuration of the PLC, because a PLC is a configuration of smaller Modules.To have a functional PLC, you would need to have CPU Rack with at least one Module mounted to it that provides I/O points. When we refer to the PLC, however, we are generally talking about the CPU and all of their Modules directly controlled by it through the program. This does not include the I/O devices connected to PLC inputs and outputs.(2) Inputs and outputsA device connected to the PLC that sends a signal to the PLC is called an input device。 the signal it sends is called an input signal. A signal enters the PLC through terminals or through pins is called an input point. This input point is allocated a location in memory that reflects its status, . ether ON or OFF. This memory location is call an input bit. The CPU, in its normal processing cycle, monitors the status of all inputs and turns ON or OFF corresponding input bits accordingly.There are also output bits in memory that are allocated to output points on Modules through which output signals are sent to output devices, . an output bit is turned ON to send a signal to an output device through an output point. The CPU periodically turns output points ON or OFF according to the status of output bits.These terms are used when describing different aspects of PLC operation. When programming, one is concerned with what information is held in memory, and so I/O bits are 鞍山科技大學本科生畢業設計(論文) 第 30 頁referred to. When talking about the Modules that connect the PLC to the controlled system and the place on these Modules where signals enter and leave the PLC. I/O points are referred to. When wiring these I/O points, the physical counterparts of the I/O points, ether terminals or connector pins, are referred to. When talking about the signals that enter or leave the PLC, one refers to input signals and output signals, or sometimes just inputs and outputs. It all depends on what aspect of PLC operation is being talked about.(3) Controlled System and Control SystemThe Control System includes the PLC and all I/O devices is uses to control an external system. A sensor that provides information to achieve control is an input device that is clearly part of the Control System. The controlled system is the external system that is being controlled by the PLC program through these I/O devices. I/O devices can sometimes be considered party of the controlled system, e. g. a motor used to drive a conveyor belt.OMRON Product TerminologyOMRON products ar